Method for electroplating a circuit board having through-holes, controller and electroplating apparatus

Abstract

This application relates to the field of electroplating technology, and provides a method, controller, and electroplating equipment for electroplating circuit boards with through holes. The method for electroplating circuit boards with through holes includes: immersing the circuit board in an electroplating solution and conveying it along a predetermined path; applying a first flow field to the circuit board to form a base plating layer on the walls of the through holes, thereby giving the circuit board a first TP value; wherein the first flow field includes multiple first directional electroplating solution flows penetrating the through holes, and the thickness of the base plating layer is within a first predetermined threshold range; applying a second flow field to the circuit board with the base plating layer, thereby giving the circuit board a second TP value; the second flow field includes multiple second directional electroplating solution flows with a second pressure difference, the second pressure difference being less than the first pressure difference of the first directional electroplating solution flows, and the second TP value being greater than the first TP value. Embodiments of this application can improve the electroplating solution exchange efficiency and deposition uniformity.

Description

Technical Field

[0001] This application belongs to the field of electroplating technology, and particularly relates to a method, controller and electroplating equipment for electroplating circuit boards with through holes. Background Technology

[0002] The trend of modern high-end electronics developing towards higher performance, higher power, smaller size and higher reliability has brought considerable challenges to the manufacturing of circuit boards, which is the basic supporting technology. How to manufacture through holes with high aspect ratio and good electroplating effect is a difficult and key point in the field of circuit board manufacturing.

[0003] In the electroplating process of high aspect ratio through-hole circuit boards, existing technologies generally employ a counter-jet method to achieve plating solution exchange. However, this single flow field control mode has inherent limitations: due to the attenuation of fluid shear force in the middle of the deep hole, the plating solution exchange efficiency exhibits an axial gradient decrease, resulting in insufficient replenishment of metal ion concentration in the middle region of the hole wall. Simultaneously, the copper deposition rate at the hole opening is significantly higher than in the middle of the hole due to continuous high-velocity plating solution scouring, forming a typical "dog bone effect." More seriously, traditional counter-jet processes create turbulent dead zones within the deep hole, causing localized plating solution stagnation and leading to more severe uneven copper deposition and void defects within the hole. Although optimizing jet pressure and adjusting nozzle angle can partially improve these problems, the boundary layer effect limits the current technology's ability to simultaneously meet the process requirements of high exchange efficiency and deposition uniformity in deep hole electroplating. Summary of the Invention

[0004] This application provides a method, controller, and electroplating equipment for electroplating circuit boards with through holes, which can improve the electroplating solution exchange efficiency and deposition uniformity.

[0005] The first aspect of this application provides a method for electroplating a circuit board with through holes, comprising: immersing the circuit board in an electroplating solution and conveying it along a predetermined path; applying a first flow field to the circuit board to form a base plating layer on the wall of the through holes, thereby giving the circuit board a first TP value; wherein the first flow field includes a plurality of first directional electroplating liquid flows penetrating the through holes, the first directional electroplating liquid flows having a first pressure difference, and the thickness of the base plating layer being within a first predetermined threshold range; applying a second flow field to the circuit board with the base plating layer, thereby giving the circuit board a second TP value; the second flow field includes a plurality of second directional electroplating liquid flows having a second pressure difference; wherein the second pressure difference is less than the first pressure difference, and the second TP value is greater than the first TP value.

[0006] In some embodiments of the first aspect, a first directional electroplating liquid flow penetrates a through hole by a first pressure difference generated at both ends of the through hole through a combined spray and suction action, the first pressure difference having a first pressure difference value; a second directional electroplating liquid flow acts on the circuit board by spraying, and forms a second pressure difference by the generated unsteady pressure gradient, the second pressure difference being within a second pressure difference range; wherein, the maximum value of the second pressure difference range is less than the first pressure difference value.

[0007] In some embodiments of the first aspect, along the conveying direction of the circuit board, adjacent first directional electroplating liquid flows have a first spacing D1 between their axial centers and flow in opposite directions, and adjacent second directional electroplating liquid flows have a second spacing D2 between their axial centers, wherein D2≤D1.

[0008] In some embodiments of the first aspect, in the first flow field, the time difference between the vias of the circuit board receiving the action of adjacent first directional electroplating liquid flows is a first time difference TD1, and the time difference between the vias of the circuit board receiving the action of adjacent first directional electroplating liquid flows is a second time difference TD2, wherein TD1≤TD2.

[0009] In some embodiments of the first aspect, the second flow field is a convective electroplating liquid flow field applied simultaneously from both sides of the circuit board thickness direction to the circuit board surface, and the second flow field acts on the entire surface of the circuit board and the vias; or, the second flow field is a unidirectional flow field applied alternately along the circuit board thickness direction, the unidirectional flow field being used to apply a directional electroplating liquid flow from only one side of the circuit board thickness direction to the other side at any given time, and the flow direction is periodically alternated.

[0010] In some embodiments of the first aspect, after applying a second flow field to a circuit board having a base plating, the method further includes: applying a third flow field to the circuit board; the third flow field being the same as the first flow field, or the third flow field being the same as the second flow field.

[0011] In some embodiments of the first aspect, a first duration T1 is applied to the circuit board by a first flow field, and a second duration T2 is applied to the circuit board having a base plating by a second flow field, wherein T1 ≤ T2.

[0012] In some embodiments of the first aspect, the through-hole electroplating method further includes: detecting the current plating thickness in the through-hole of the circuit board; and controlling the circuit board to move along the conveying direction according to the current plating thickness to switch between a first flow field and a second flow field.

[0013] In some embodiments of the first aspect, detecting the current plating thickness in a via of a circuit board includes: periodically performing a first detection on the plating thickness of the via wall when the circuit board is in the region of action of a first flow field; and periodically performing a second detection on the plating thickness of the via wall when the circuit board is in the region of action of a second flow field.

[0014] In some embodiments of the first aspect, controlling the circuit board to move along the conveying direction according to the current plating thickness specifically includes: if the first detected plating thickness is lower than the lower limit of a first predetermined threshold range, controlling the circuit board to reduce the conveying speed or suspend conveying; if the first detected plating thickness is higher than the upper limit of the first predetermined threshold range, controlling the circuit board to increase the conveying speed.

[0015] In some embodiments of the first aspect, a buffer zone is provided between adjacent flow fields along the conveying direction of the circuit board. The buffer zone includes: an upstream flow baffle plate, located downstream of the previous flow field region, for blocking the transmission of pressure fluctuations; a downstream flow equalizer plate, located upstream of the subsequent flow field region, for equalizing the electroplating liquid flow entering the subsequent flow field; and a pressure buffer chamber, formed between the upstream flow baffle plate and the downstream flow equalizer plate, for buffering pressure fluctuations.

[0016] In some embodiments of the first aspect, the method further includes applying a forward-reverse switching current to the circuit board, the forward-reverse switching current comprising an alternately applied forward plating current and a reverse pulse current.

[0017] In some embodiments of the first aspect, the forward-reverse switching current is synchronized with the application timing of the first or second flow field, wherein: when the first flow field is applied, the forward-reverse switching current operates with a first forward current density, a first reverse current density, a first frequency, a first forward pulse width, and a first reverse pulse width; when the second flow field is applied, the forward-reverse switching current operates with a second forward current density, a second reverse current density, a second frequency, a second forward pulse width, and a second reverse pulse width. The first forward current density is less than the second forward current density.

[0018] In some embodiments of the first aspect, the first reverse current density is 1 to 5 times the first forward current density, and the pulse width of the first forward pulse current is 5 to 20 times the pulse width of the first reverse pulse current.

[0019] In some embodiments of the first aspect, the first flow field is formed by controlling the parameter conditions of the spray units and suction units staggered on both sides of the thickness direction of the circuit board, so that the spray units and suction units on both sides are arranged in a spray-suction correspondence, and the electroplating liquid flow sprayed from one side of the spray unit passes through the through hole under the spray-suction pressure difference and is sucked in by the corresponding suction unit on the opposite side to form a directional electroplating liquid flow; along the conveying direction of the circuit board, adjacent spray units and suction units are staggered so that the flow directions of adjacent directional electroplating liquid flows are opposite.

[0020] In some embodiments of the first aspect, the second flow field is formed by controlling multiple sets of spray units symmetrically arranged on both sides of the thickness direction of the circuit board to simultaneously spray electroplating liquid onto the surface of the circuit board, forming a double-sided convective electroplating liquid flow field, wherein the nozzles on the spray units on both sides are staggered in the thickness direction of the circuit board.

[0021] In some embodiments of the first aspect, the second flow field is formed by means of timing control, causing the spray units arranged on both sides of the circuit board in the thickness direction to work alternately, such that at any given time only one spray unit sprays electroplating liquid onto the surface of the circuit board, while the spray unit or suction unit on the other side is in a closed or suction state, thereby forming a unidirectional flow field with periodically alternating flow direction.

[0022] In some embodiments of the first aspect, the base coating is a continuous conductive layer with a thickness of at least 0.5 μm.

[0023] In some embodiments of the first aspect, the aspect ratio of the through hole ranges from 20:1 to 50:1.

[0024] A second aspect of this application provides a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the above-described method for electroplating a circuit board with through holes.

[0025] A third aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method for electroplating a circuit board with through-holes.

[0026] A fourth aspect of this application provides a computer program product that, when run, causes the above-described electroplating method for a circuit board with through holes to be executed.

[0027] The fifth aspect of this application provides an electroplating apparatus, comprising: an electroplating device including a first processing section and a second processing section arranged sequentially along the conveying direction of the circuit board; the first processing section being used to form a first flow field, and the second processing section being used to form a second flow field; and a controller connected to the electroplating device for performing the steps of the electroplating method for a circuit board having through holes as described in any of the first aspects.

[0028] The sixth aspect of this application provides a circuit board including an interconnect structure, wherein the interconnect structure is obtained by electroplating a circuit board with through holes according to any one of the first aspects, or is made based on the electroplating equipment described in the fifth aspect.

[0029] In the embodiments of this application, the circuit board is immersed in an electroplating solution and transported along a predetermined path. A first flow field is applied to the circuit board to form a continuous base plating layer on the walls of the through holes, giving the circuit board a first TP value. The first flow field includes multiple first directional electroplating liquid flows penetrating the through holes, and the first directional electroplating liquid flows have a first pressure difference. The higher first pressure difference can improve the electroplating solution exchange efficiency and ensure the discharge of air bubbles in the holes. Subsequently, a second flow field is applied to the circuit board with the base plating layer to give the circuit board a second TP value. The second flow field includes multiple second directional electroplating liquid flows with a second pressure difference, and the second pressure difference is less than the first pressure difference. The non-steady electroplating liquid flow caused by the reduced pressure difference can make the thickness of the thinnest part in the hole gradually catch up with the board surface, improving the overall deposition uniformity, and thus increasing the TP value of the circuit board to a higher second TP value. Therefore, compared with the traditional single flow field application technique, the electroplating solution exchange efficiency and the overall deposition uniformity of the plating layer are improved, and the deep plating capability for high aspect ratio through holes is effectively improved. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram illustrating the implementation process of an electroplating method for a circuit board with through holes, provided in an embodiment of this application. Figure 2 This is a schematic diagram of the first flow field provided in an embodiment of this application; Figure 3 This is a schematic diagram of a local microflow field provided in an embodiment of this application; Figure 4 This is a schematic diagram of the first type of second flow field provided in the embodiments of this application; Figure 5 This is a schematic diagram of the second type of second flow field provided in the embodiments of this application; Figure 6 This is a schematic diagram of the buffer provided in an embodiment of this application; Figure 7 This is a schematic diagram of the electroplating effect of the circuit board provided in the embodiments of this application; Figure 8 This is a schematic diagram of the controller provided in an embodiment of this application; Figure 9 This is a schematic diagram of the electroplating equipment provided in the embodiments of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are protected by this application.

[0033] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0034] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] References to "one embodiment" or "some embodiments" in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0036] Existing technologies generally employ a contralateral jetting method to achieve plating solution exchange, but this single flow field control mode has inherent limitations: due to the attenuation of fluid shear force in the middle of the deep hole, the plating solution exchange efficiency exhibits an axial gradient decrease, resulting in insufficient replenishment of metal ion concentration in the middle region of the hole wall. Simultaneously, the orifice region, continuously subjected to high-velocity plating solution scouring, exhibits a significantly higher copper deposition rate than the middle region, forming a typical "dog-bone effect." More seriously, traditional contralateral jetting creates turbulent dead zones within the deep hole, causing localized plating solution stagnation and leading to more severe copper deposition inhomogeneity and void defects within the hole. Although optimizing jet pressure and adjusting nozzle angle can partially improve these problems, the boundary layer effect limits the ability of existing technologies to simultaneously meet the process requirements of high exchange efficiency and deposition uniformity in deep-hole electroplating. Therefore, this application employs a staged electroplating process, improving both plating solution exchange efficiency and deposition uniformity.

[0037] To illustrate the technical solution of this application, specific embodiments are described below.

[0038] Figure 1 The illustration shows a schematic diagram of the implementation process of an electroplating method for a circuit board with through holes according to an embodiment of this application. This method can be applied to a controller.

[0039] The aforementioned circuit board may include one or more of the following: printed circuit board (PCB), flexible printed circuit (FPC), rigid-flex board, high-density interconnect (HDI), integrated circuit substrate, metal core PCB, glass substrate, and ceramic substrate. The circuit board may have several through-holes, particularly high aspect ratio through-holes. A high aspect ratio refers to the aspect ratio (the ratio of hole depth to hole diameter) of the through-hole being greater than a preset threshold. Specifically, the aspect ratio of high aspect ratio through-holes ranges from 20:1 to 50:1; this application uses an aspect ratio of 40:1 as an example.

[0040] Specifically, the above-mentioned electroplating method for circuit boards with high aspect ratio through holes may include the following steps S101 to S103.

[0041] Step S101: Immerse the circuit board in the electroplating solution and transport it along a predetermined path.

[0042] Specifically, the circuit board can be gradually immersed in an electroplating bath containing electroplating solution at a preset angle, and eventually completely submerged in the solution. Immersing the circuit board in the electroplating solution ensures that all surfaces of the circuit board (including the board surface and hole walls) come into contact with the solution. This allows copper layers to be deposited under the influence of an electric field after power is applied, preventing defects such as open circuits or no copper in holes caused by the inability to deposit metal on parts exposed above the liquid surface.

[0043] After the circuit board is fully submerged, it can be transported along a predetermined path. This predetermined path refers to the pre-defined motion trajectory within the electroplating equipment used to transport the circuit board. Along this predetermined path, several flow fields (at least including the first and second flow fields described below) can be sequentially set up to apply controllable hydrodynamic forces to the surface of the circuit board immersed in the electroplating solution, improving the exchange efficiency and deposition effect of the electroplating solution within the holes. Specifically, the transport of the circuit board can be achieved through the coordinated action of a drive device (such as a servo motor or chain drive) and a guide rail system (such as a linear guide or roller guide): the drive device provides the power to move along the predetermined path and limits the moving speed, while the guide rail limits the running direction and attitude of the circuit board, ensuring its smooth and precise passage through the areas of influence of each flow field.

[0044] Step S102: Apply a first flow field to the circuit board to form a base plating layer on the wall of the through hole of the circuit board, thereby giving the circuit board a first TP value.

[0045] Specifically, during the transport of the circuit board along the path, it first passes through the area of ​​action of the first flow field. This area applies a first flow field to the circuit board, which includes directional electroplating liquid flows through multiple through-holes, and these directional electroplating liquid flows have a first pressure difference. Specifically, within each of the first directional electroplating liquid flows, the electroplating liquid enters on one side of the circuit board's thickness direction and exits on the opposite side, creating a first pressure difference between the two sides of the circuit board's thickness direction. Under the action of the first pressure difference, the electroplating liquid can actively flow from the side where it enters to the opposite side, thus penetrating the through-holes. Deposition can occur in the through-holes as they pass through each directional electroplating liquid flow, and a base plating layer can be deposited after passing through the entire area of ​​action of the first flow field. The base plating layer is a plating layer attached to the wall of the through-hole, and its thickness is within a first predetermined threshold range. At this time, the thickness of the base plating layer within the circuit board allows it to have a first TP value.

[0046] TP value refers to Throwing Power, which can be expressed as: TP value (%) = (Thinnest copper thickness inside the hole / Copper thickness on the board surface) × 100%. The higher the TP value, the closer the thickness of the metal layer plated on the inner wall of the hole is to the thickness of the metal layer on the board surface. The first TP value is the TP value of the circuit board after the action of the first flow field (forming the base plating layer).

[0047] It should be noted that the first predetermined threshold range can be set according to the actual situation. For example, the first predetermined threshold range can be greater than 1 / 50 of the coating in the target hole and 1 / 5 of the coating in the target hole. For example, when the coating thickness in the target hole is 25um, the maximum thickness of the base coating can be 5um and the minimum thickness can be 0.5um.

[0048] Step S103: Apply a second flow field to the circuit board with the base plating to give the circuit board a second TP value.

[0049] In embodiments of this application, during the transport of the circuit board along the path, after leaving the area of ​​effect of the first flow field, it can enter the area of ​​effect of the second flow field. This area of ​​effect can apply the second flow field to the circuit board with the base plating layer. The second flow field may include multiple second directional electroplating liquid flows with a second pressure difference, wherein the second pressure difference is less than the first pressure difference, and the second TP value is greater than the first TP value.

[0050] Specifically, during the process of immersing the circuit board in the electroplating solution, air can easily remain in the through-holes. For high aspect ratio circuit boards, it is necessary to first ensure that the air in the holes is expelled and that the electroplating solution is completely filled. Therefore, within the area of ​​the first flow field, a higher first pressure difference forces the electroplating solution to penetrate the through-holes, forcibly renewing the electroplating solution within the holes. This allows for the replacement of the plating solution and the removal of air bubbles in a very short time, preventing blind holes or residual air bubbles on the hole wall that would result in no copper inside the holes. At the same time, it delivers fresh metal ions to the deepest part of the holes in a very short time, establishing a continuous base plating layer. As the base plating layer is formed and the circuit board reaches the first TP value, in order to ensure the uniformity of the plating layer, it is necessary to switch to a second flow field with a smaller pressure difference (i.e., a second pressure difference). Because the pressure difference across the thickness of the circuit board is reduced, a gentler and more uniform fluid shear force allows additives in the electroplating solution (including brighteners, inhibitors, and leveling agents) to be distributed more evenly within the holes, continuously delivering ions into the holes. The leveling agent forms an adsorption film at the hole opening, which is not easily washed away by the smaller pressure difference in the electroplating solution, inhibiting copper ion reduction and effectively suppressing hole growth. As a result, the thickness of the thinnest part within the hole (usually at the hole center) gradually catches up with the board surface, and the total pressure (TP) value gradually increases from a lower first TP value to a second TP value, significantly mitigating the "dog bone effect." The second TP value is the TP value reached by the circuit board after leaving the area affected by the second flow field.

[0051] In the embodiments of this application, the circuit board is immersed in an electroplating solution and transported along a predetermined path. A first flow field is applied to the circuit board to form a continuous base plating layer on the walls of the through holes, giving the circuit board a first TP value. The first flow field includes multiple first directional electroplating liquid flows penetrating the through holes, and the first directional electroplating liquid flows have a first pressure difference. The higher first pressure difference can improve the electroplating solution exchange efficiency and ensure the discharge of air bubbles in the holes. Subsequently, a second flow field is applied to the circuit board with the base plating layer to give the circuit board a second TP value. The second flow field includes multiple second directional electroplating liquid flows with a second pressure difference, and the second pressure difference is less than the first pressure difference. The unsteady electroplating liquid flow caused by the reduced pressure difference can make the thickness of the thinnest part in the hole gradually catch up with the board surface, improving the overall deposition uniformity, and thus increasing the TP value of the circuit board to a higher second TP value. Therefore, compared with the traditional single flow field application technique, the electroplating solution exchange efficiency and the overall deposition uniformity of the plating layer are improved, and the deep plating capability for high aspect ratio through holes is effectively improved.

[0052] In some embodiments of this application, in a first flow field, a first directional electroplating liquid flow can penetrate a through hole through a first pressure difference generated at both ends of the through hole by a combined spray and suction action.

[0053] In other words, for each first directional electroplating solution flow, the electroplating solution can be sprayed along one side of the through hole and sucked up on the other side. This combined spraying and suction creates a first pressure difference, causing the electroplating solution to actively flow from one side of the through hole to the other under the influence of this first pressure difference. The first pressure difference has a first pressure difference value, the magnitude of which can be adjusted by modifying the spraying and suction parameters according to actual needs.

[0054] In some embodiments of this application, along the conveying direction of the circuit board, adjacent first directional electroplating liquid flows have a first distance D1 between their axial centers and flow in opposite directions. The axial center can refer to the mainstream direction of the first directional electroplating liquid flow, and the trajectory line determined on each cross-section according to the maximum axial velocity (or momentum flux weighted center).

[0055] Specifically, along the conveying direction of the circuit board, adjacent first directional electroplating liquid flows have opposite directions. When the circuit board moves along a predetermined path, the vias can be alternately penetrated by first directional electroplating liquid flows with different directions, and deposition can occur. Adjacent first directional electroplating liquid flows can be spaced apart by a first gap D1 to avoid mutual interference between adjacent first directional electroplating liquid flows.

[0056] It is understandable that when a unidirectional fluid encounters micro-roughness of the orifice wall, residual impurities, or air bubbles, a flow dead zone may form on its downstream side. Alternating reverse flows can flush from the other side, covering the area that the previous direction failed to effectively act, ensuring that every point on the orifice wall has undergone effective flushing in at least one direction.

[0057] In some specific embodiments, the first flow field can be formed in the following way: the parameters of the spray units and suction units arranged alternately on both sides of the thickness direction of the circuit board are controlled so that the spray units and suction units on both sides are arranged in a spray-suction correspondence, and the electroplating liquid flow sprayed from one side of the spray unit passes through the through hole under the spray-suction pressure difference and is sucked in by the corresponding suction unit on the opposite side to form a directional electroplating liquid flow; along the conveying direction of the circuit board, adjacent spray units and suction units are arranged alternately so that the flow directions of adjacent directional electroplating liquid flows are opposite.

[0058] The spray unit and suction unit set in the first flow field can be referred to as the first spray unit and the first suction unit. It can be understood that by controlling and adjusting the parameter conditions of the first spray unit and the first suction unit on both sides, such as pressure, flow rate, divergence angle, and the distance between the first spray unit and the corresponding first suction unit, the electroplating liquid flow sprayed from the first spray unit can be driven by the first pressure difference to pass through the through hole and be sucked in by the corresponding first suction unit on the opposite side, forming a first directional electroplating liquid flow. For example, the distance between the corresponding first spray unit and suction unit on the opposite side can be reduced, and / or the spray positive pressure and suction negative pressure can be increased, and / or the emission angle of the first spray unit can be reduced, so that the electroplating liquid sprayed by the first spray unit can be directionally penetrated through the through hole, forming a uniform base coating on the hole wall.

[0059] Along the conveying direction of the circuit board, adjacent spray units and suction units are staggered to ensure that the flow directions of adjacent first directional electroplating liquid flows are opposite. For example, along the same side of the circuit board, the first spray units and first suction units are arranged alternately, so that adjacent first directional electroplating liquid flows flow in opposite directions, causing the through holes to be alternately penetrated by directional electroplating liquid flows with different directions. The distance between adjacent spray units and suction units is 5mm-50mm. A preferred distance is 25mm to 30mm.

[0060] Please refer to Figure 2The diagram illustrates that, under the negative pressure generated by the suction unit, the electroplating solution in each first directional electroplating solution flowes through the through-hole to one side of the suction unit. This forced through-flow field accelerates the replacement of the electroplating solution within the hole, eliminating the electroplating solution stagnation in the middle of the through-hole caused by traditional contralateral jetting. This ensures that the hole wall is in contact with fresh electroplating solution throughout, guaranteeing a sufficient supply of copper ions and timely replacement reaction in the middle of the through-hole. This helps prevent the formation of voids in the middle of the through-hole and also avoids premature closure of the orifice due to rapid deposition at the orifice opening, thus exacerbating hollowing. By alternating the flow direction of multiple directional electroplating solution flows, the flow direction of the electroplating solution through the through-hole can be periodically reversed over time, so that each through-hole receives the through-flow action of frequent directional changes. During electroplating, the spray side of the plating solution experiences faster deposition due to a more abundant ion supply. By periodically reversing the flow direction, the vias of the circuit board are sequentially swept by bidirectional through-flow in both forward and reverse directions during transport. This eliminates stagnant dead zones within the vias and ensures consistent deposition rates at both ends in a time-averaged sense, effectively suppressing the problem of asymmetry. Furthermore, it balances the stress on both sides of the circuit board, preventing stress imbalances caused by unilateral spraying and suction, ensuring a uniform and continuous base plating layer forms on the via wall from inlet to outlet. While the first flow field helps form a uniform base plating layer in the vias, the presence of the suction unit concentrates the fluid shear force at the inlet. In the central region of the via, the fluid velocity rapidly decreases due to frictional resistance, creating a region with insufficient laminar or even turbulent flow, failing to break through the boundary layer. This results in slower ion replenishment and additive exchange rates in the central region compared to the via opening, limiting the plating formation rate in the central region and hindering uniform copper growth on the circuit board surface.

[0061] To address this issue, a second flow field can be applied after the circuit board has formed a base plating layer and reached the first TP value.

[0062] In some embodiments of this application, the second directional electroplating liquid flow acts on the circuit board by spraying, and a second pressure difference is formed by the generated unsteady pressure gradient.

[0063] The unsteady pressure gradient refers to a pressure that changes simultaneously with time and space along the fluid flow direction, rather than remaining constant. This unsteady pressure gradient generates weak pressure fluctuations within the pore, preventing excessive adsorption of the leveling agent at the pore opening and enhancing ion transport efficiency. The unsteady pressure gradient creates a second pressure difference, ensuring that this second pressure difference falls within a certain range, with its maximum value being less than the first pressure difference. This creates a dynamic and unstable pressure field on both sides of the plate surface. Compared to the forced, rapid, and stable first flow field penetrating the pore, the unsteady pressure gradient of this second flow field generates stronger turbulence within the pore, more effectively breaking down the diffusion boundary layer in the central region. This allows the copper ion concentration and additive concentration at the pore center to be maintained at levels close to the plate surface, ensuring deposition in the central region. Consequently, the deposition rate within the pore increases, and the TP value significantly increases.

[0064] In some embodiments of this application, the second flow field can be a convective electroplating solution flow field applied simultaneously from both sides of the circuit board thickness direction to the circuit board surface, and the second flow field acts on the entire circuit board surface and through holes.

[0065] In other words, electroplating solution can be sprayed simultaneously on both sides along the thickness direction of the circuit board, and the electroplating solution sprayed on both sides can form a second flow field with opposing flow.

[0066] Specifically, the second flow field can be formed in the following way: multiple sets of spray units symmetrically arranged on both sides of the thickness direction of the circuit board simultaneously spray electroplating liquid onto the surface of the circuit board to form a double-sided convective electroplating liquid flow field, and the nozzles on the spray units on both sides are staggered in the thickness direction of the circuit board.

[0067] For example, a first spray module and a second spray module can be configured along both sides of the circuit board thickness direction. The first and second spray modules each include multiple second and third spray units arranged at intervals along the conveying direction. The second and third spray units can be configured in a staggered arrangement. The first and second spray modules are connected to the liquid supply system through independent liquid supply pipelines, enabling individual on / off control. Thus, the first and second spray modules can work synchronously at the same time, forming a second flow field. In another embodiment, the second and third spray units can be configured to face each other. For example, in electroplating circuit boards with low aspect ratios or high requirements for stress balance on both sides, the spray units can also be arranged facing each other.

[0068] Because the nozzles on both sides are misaligned, a static pressure balance will not be formed on both sides of the circuit board. Instead, periodic pressure fluctuations will occur, forming the aforementioned unsteady pressure gradient.

[0069] Please refer to Figure 4The opposing flow fields create independent impact zones on both sides of the circuit board. Under pressure, the electroplating solution continuously washes the board surface and through-holes. At this time, a small portion of the sprayed electroplating solution enters the through-holes, while a larger portion flows laterally out along the board surface. Utilizing the high mass transfer characteristics of the high-speed jet flow field, a high-concentration ion supply zone and a rapid deposition environment can be formed on both sides of the circuit board and in the through-holes, achieving rapid coating thickness increase. By utilizing pressure fluctuations, the diffusion boundary layer in the center region of the hole can be broken. At the same time, due to the presence of the base coating, normal ion diffusion and deposition processes can still be maintained within the through-holes under the drive of the concentration gradient, allowing the copper ion concentration and additive concentration in the center of the hole to be maintained at levels close to those on the board surface. Figure 4 In this design, the nozzles on the spray units on both sides are staggered along the thickness direction of the circuit board. All spray units simultaneously spray electroplating solution onto both sides of the circuit board, and the projections of the spray positions on both sides along the thickness direction do not overlap, thus creating a spatially staggered distribution between the spray units. This staggered arrangement avoids head-on collisions between the jets near the circuit board surface, preventing excessive turbulence or energy cancellation. Instead, it allows the jets on both sides to form relatively independent impact zones on the circuit board surface, creating opposing crossflows near the board surface. This more effectively breaks the diffusion boundary layer in the hole center region, facilitating uniform coverage of the flow field on the board surface while maintaining a high mass transfer rate.

[0070] In some other embodiments of this application, the second flow field is a unidirectional flow field that is applied alternately along the thickness direction of the circuit board. The unidirectional flow field is used to apply a directional electroplating liquid flow from one side to the other side of the thickness direction of the circuit board at any given time, and the flow direction is periodically switched.

[0071] In other words, electroplating solution can be sprayed from both sides along the thickness direction of the circuit board. Part of the sprayed solution enters the via, while the rest flows laterally out along the board surface. Through temporal misalignment, uniform laminar flows perpendicular to the board surface are formed on both sides, resulting in a circuit board with high surface copper thickness uniformity. When the flow direction switches, the pressure gradient inside the via instantly reverses, generating a pressure pulsation wave, thus forming the aforementioned unsteady pressure gradient. Simultaneously, due to the presence of the base plating layer, normal ion diffusion and deposition processes can still be maintained within the via under the drive of the concentration gradient, and compared to the first flow field, it exhibits better mass transfer at the via center.

[0072] Specifically, the second flow field can be formed in the following way: by timing control, the spray units set on both sides of the circuit board in the thickness direction work alternately. At any given time, only one side of the spray unit sprays electroplating liquid onto the circuit board surface, while the other side's spray unit or suction unit is in a closed or suction state, thereby forming a unidirectional flow field with periodically alternating flow direction.

[0073] Specifically, the aforementioned first and second spray modules can operate independently at different times, alternately forming a unidirectional flow field. Please refer to [reference needed]. Figure 5 A unidirectional flow field can form a flow field covering the entire thickness direction on one side of the circuit board, and after a certain period of time switch to forming a flow field covering the entire thickness direction only on the opposite side. This flow field can improve the deep plating capability of high aspect ratio vias and form a stable diffusion layer thickness on the board surface. The alternating unidirectional flow field on one side creates a stable unidirectional pressure difference in the thickness direction of the circuit board. This pressure difference drives fresh electroplating solution to cover the entire via section along the base plating layer, continuously replenishing copper ions and removing reaction byproducts, so that the plating growth rate in the middle of the via tends to be consistent with that at the via opening. By controlling the timing to achieve periodic flow direction switching, the via openings at both ends can alternately serve as the inlet and outlet of the flow field, completely eliminating the plating deviation at the inlet and outlet ends caused by unidirectional flow, helping to balance the copper deposition rate at both ends, achieving uniform growth throughout the via section, and significantly improving the TP value of the circuit board. At the same time, the unidirectional flow field provides ideal hydrodynamic conditions for the uniform growth of surface copper, ultimately improving the thickness uniformity and microstructure density of the surface copper.

[0074] The unidirectional flow field can be formed by superimposing multiple unidirectional sub-flow fields, with the electroplating solution flow rate and spray pressure of each sub-flow field meeting predetermined thresholds. These unidirectional sub-flow fields superimpose in space, canceling out local velocity differences and forming a parallel flow field covering the entire surface with uniform velocity. During alternating spraying, the electroplating solution continuously washes the plate surface in a vertical direction, ensuring uniform fluid impact force across all areas of the orifice.

[0075] In some embodiments of this application, a second spacing D2 exists between the axial centers of adjacent second directional electroplating liquid flows, where D2 ≤ D1. Specifically, the second spacing D2 determines the frequency of pressure changes. Compared to the first flow field, reducing the nozzle spacing (i.e., D2 ≤ D1) means arranging more spray units per unit length, with each nozzle covering a smaller area and a finer flow field. This avoids some holes from not receiving effective scouring due to being located in the gap between two jets, ensuring spatial uniformity of ion supply and thus improving deposition uniformity.

[0076] In some embodiments of this application, the time difference between the adjacent first directional electroplating liquid flows acting on the through-hole of the circuit board is a second time difference TD2, where TD1≤TD2. Thus, by increasing the time difference, the pressure pulsation frequency is reduced, thereby lowering the shear force and preventing the leveling agent from being washed away. Simultaneously, the duration of each flow direction is allowed to be sufficiently long, enabling the establishment of a stable ion concentration gradient and additive distribution within the hole.

[0077] After passing through the second flow field, a circuit board that meets the preset TP value can be formed on the basis of the base plating. In some embodiments of this application, the TP value of the circuit board can be guaranteed by setting a second action duration T2 for the second flow field on the circuit board with the base plating. Where T1≤T2, the air bubbles are quickly discharged through the short first flow field, and then a uniform plating layer is formed through the longer second flow field.

[0078] In some embodiments of this application, after applying a second flow field to a circuit board having a base plating, the application may further include: applying a third flow field to the circuit board; the third flow field being the same as the first flow field, or the third flow field being the same as the second flow field.

[0079] In other words, after applying the first and second flow fields to the circuit board to be electroplated, a third flow field identical to the first or second flow field can be applied to further improve the uniformity of the plating layer inside the holes, avoid the deviation of the through-hole plating layer caused by uneven current on the board surface, optimize the overall uniformity, and at the same time flatten the protruding plating layer at the opening of the through holes. Ultimately, high TP value and high board surface uniformity are achieved simultaneously, which helps to obtain a high-quality, high aspect ratio interconnect structure with improved plating uniformity, so as to meet the process requirements of high-density interconnect circuit boards in fields such as 5G communication equipment and high-performance servers.

[0080] In practical applications, in order to ensure that the plating layer meets the processing requirements, in some embodiments, the through-hole electroplating method may further include: detecting the current plating thickness in the through-hole of the circuit board; and controlling the circuit board to move along the conveying direction according to the current plating thickness, so as to switch between a first flow field and a second flow field.

[0081] The current plating thickness refers to the real-time thickness of the plating layer covering the circuit board during the electroplating process. In some embodiments, an insertable microprobe can be placed on the rack that transports the circuit board to move synchronously with the circuit board and collect the current plating thickness formed in various flow fields as the circuit board moves along the transport direction.

[0082] Specifically, when the circuit board is in the area of ​​the first flow field, the thickness of the plating on the wall of the via can be periodically detected. If the thickness of the base plating is detected to be within a first predetermined threshold range, the circuit board can be controlled to maintain a predetermined conveying speed along the conveying direction to allow it to enter the second flow field. If the first detected plating thickness is lower than the lower limit of the first predetermined threshold range, the circuit board can be controlled to reduce the conveying speed or pause the conveying to increase the duration of the first flow field application until the target plating thickness is reached, allowing it to switch to the second flow field more slowly. If the first detected plating thickness is higher than the upper limit of the first predetermined threshold range, the circuit board can be controlled to increase the conveying speed to reduce the duration of the first flow field application, allowing it to switch to the second flow field more quickly.

[0083] Specifically, a first inspection station can be set up in the area of ​​effect of the first flow field to obtain the basic plating thickness of the through-hole wall when the circuit board reaches the first inspection station. H 1. The controller will set the first predetermined threshold range [ Hmin , Hmax ]and H 1. Comparison: If H 1< Hmin This indicates that the base coating is too thin and a continuous conductive network has not yet formed on the hole walls. In this case, the controller will perform the following actions: reduce the conveying speed of the conveying mechanism to extend the residence time of the circuit board in the first flow field area; or pause the conveying and resume it once the thickness meets the standard; simultaneously, it can provide feedback to the control system to appropriately increase the spray pressure or current density of the first flow field to accelerate the formation of the base coating. H 1> Hmax This indicates that the base plating layer is too thick, which may affect production efficiency or lead to excessive deposition at the orifices. In this case, the controller increases the conveyor speed and shortens the residence time of the circuit board in the first flow field region. If Hmin ≤ H 1≤ Hmax If the thickness of the base coating meets the requirements, the controller maintains the current conveying speed and triggers the flow field switching command, causing the circuit board to enter the action area of ​​the second flow field.

[0084] Similarly, based on the current coating thickness, the control board moves along the conveying direction to switch between the second and third flow fields.

[0085] Specifically, during the process of the circuit board being in the area of ​​the second flow field, the plating thickness of the via wall can be detected for the second time. If the plating thickness of the via is within the range of the second predetermined threshold, it indicates that the via is basically plated. At this time, the circuit board can be moved along the conveying direction to allow it to enter the third flow field. If the plating thickness detected by the second step is lower than the lower limit of the second predetermined threshold range, the circuit board is controlled to reduce the conveying speed or pause the conveying to increase the duration of the second flow field application until the target plating thickness is reached, allowing it to switch to the third flow field more slowly. If the plating thickness detected by the second step is higher than the upper limit of the second predetermined threshold range, the circuit board is controlled to increase the conveying speed to reduce the duration of the second flow field application, allowing it to switch to the third flow field more quickly.

[0086] Specifically, after the circuit board enters the second flow field, the second inspection station obtains the thickness of the thickened plating layer on the wall of the through hole. H 2. The controller determines the target thickness. H target Adjust for deviations from the measured thickness: If H 2< H targetInsufficient thickness: The controller reduces the conveyor speed or pauses the conveyor, extending the electroplating time. H2≥H target Once the thickness reaches the standard, the controller triggers a process end command, and the circuit board is transported to the area of ​​action of the third flow field.

[0087] In some embodiments of this application, the thickness of the base coating can be... H When the predetermined threshold is reached, the system immediately switches to the second flow field. This method is simple to control and suitable for scenarios with a wide process window.

[0088] To ensure a smooth transition of the electroplating solution, a soft switching based on position and thickness can be implemented: a buffer zone is set between adjacent flow fields. When the detected thickness approaches a threshold, the intensity of the first flow field is gradually reduced, while the intensity of the second flow field is gradually increased, achieving a smooth transition and avoiding pressure shocks. Alternatively, a thickness-time model can be established based on historical data to predict the optimal switching point, combining feedforward and feedback control.

[0089] In addition, to ensure the reliability of the closed-loop control system, this embodiment can adopt at least one of the following fault-tolerant designs, including: ① Multi-hole detection: Each detection station detects multiple through holes on the circuit board (e.g., 2-3 selected from the board edge, board center, and board corner), and takes the average value as a representative value to avoid misjudgment caused by local anomalies; ② Redundant detection: Two sets of detection devices are set up at key detection stations. When the main detection device fails or the data is abnormal, it automatically switches to the backup detection device; ③ Alarm and intervention: When the detection result exceeds the process limit range (e.g., the base plating thickness is less than 0.3μm) or the detection data changes abruptly, the control system issues an audible and visual alarm and suspends the conveying process, requiring operator intervention.

[0090] By monitoring the coating thickness in real time and dynamically adjusting the conveyor speed, it is ensured that each circuit board enters the next flow field at the optimal time, and that each circuit board leaves the first flow field with a continuous conductive network formed in its via walls. This fully leverages the "basic conductivity" function of the first flow field and the "efficient thickening" function of the second flow field. Furthermore, dynamically adjusting the conveyor speed avoids excessive dwell time on the circuit boards, improving equipment utilization.

[0091] When a third flow field needs to be applied to the circuit board, the plating thickness of the via wall can also be measured during the process of the circuit board being within the area of ​​the third flow field. The process of the third measurement can refer to the process of the second measurement, and will not be described in detail in this application.

[0092] In other embodiments, the circuit board can be controlled to move along the conveying direction according to the duration of the flow fields, switching between the first, second, and third flow fields. The specific duration of each flow field can be adjusted based on the circuit board's structure (thickness, size, number of vias) or the speed at which the circuit board moves along a predetermined path within each flow field. For example, the duration ratio of the first, second, and third flow fields is 3:10:3 throughout the entire electroplating cycle. Thus, by assigning a larger proportion of duration to the second flow field, rapid thickness increase can be achieved to improve electroplating efficiency.

[0093] It should be noted that, as Figure 6 As shown, in order to avoid mutual interference between different flow fields, in some embodiments of this application, a buffer zone is provided between adjacent flow fields along the conveying direction of the circuit board to isolate pressure fluctuations and flow pattern interference between adjacent flow fields and ensure that different flow field regions operate independently and stably.

[0094] Specifically, the aforementioned buffer zone may include an upstream baffle plate, a downstream flow equalization plate, and a pressure buffer chamber. The upstream baffle plate and / or the downstream flow equalization plate are provided with pressure balancing holes, such as honeycomb holes.

[0095] An upstream baffle plate is positioned downstream of the preceding flow field region. Taking the preceding flow field region as the first flow field as an example, the upstream baffle plate is adjacent to the formation area of ​​the first flow field. Taking the preceding flow field region as the second flow field as an example, the upstream baffle plate is adjacent to the formation area of ​​the second flow field. The upstream baffle plate is a vertically arranged plate structure made of corrosion-resistant, non-conductive material (such as PVC or PP), with a thickness of 8mm to 15mm. The upstream baffle plate includes two plates spaced apart along the width of the electroplating tank and vertically spaced to accommodate the passage of the circuit board. Its bottom end is 50mm to 100mm away from the bottom of the electroplating tank, and its top end is higher than the surface of the electroplating solution, thus preventing pressure fluctuations generated in the spray suction area of ​​the preceding flow field region from being transmitted downstream.

[0096] The downstream flow equalization plate is located upstream of the next flow field region. Taking the next flow field region as the second flow field as an example, the downstream flow equalization plate is adjacent to the second flow field formation region. Taking the next flow field region as the third flow field as an example, the upstream flow barrier is adjacent to the third flow field formation region. The downstream flow equalization plate is also a vertically arranged plate structure, made of the same material as the upstream flow barrier, and has the same gaps. Multiple through holes are evenly distributed on the downstream flow equalization plate, with diameters ranging from 5mm to 15mm and an opening ratio of 30% to 50%. The function of the downstream flow equalization plate is to homogenize the electroplating solution flow entering the next flow field region. The electroplating solution from the buffer chamber may have localized flow velocity unevenness or turbulence. After being throttled by the through holes of the downstream flow equalization plate, the flow field is regulated into a uniform laminar or low-turbulence flow, providing stable inlet conditions for the next flow field region.

[0097] A pressure buffer chamber is formed in the space between the upstream baffle plate and the downstream flow equalization plate, with a width of 100mm to 200mm along the conveying direction. The pressure buffer chamber is filled with electroplating solution. When upstream pressure fluctuations are transmitted to the buffer chamber, the pressure fluctuation amplitude is significantly attenuated due to the large volume and compressibility of the electroplating solution within the chamber. An overflow port can be provided at the top of the pressure buffer chamber, and the height of the overflow port is adjustable. When the chemical circulation volume fluctuates, excess chemical solution can be quickly discharged through the overflow port, thereby buffering pressure fluctuations and maintaining stable liquid level and pressure in the buffer chamber.

[0098] In some other embodiments, a rectifier is provided upstream of the downstream flow equalization plate to further ensure the uniformity of the subsequent flow field. The rectifier can be a honeycomb structure composed of multiple parallel hexagonal or circular channels, with a channel length-to-diameter ratio (L / D) greater than or equal to 5. The rectifier is integrally molded from a corrosion-resistant material (such as PP or CPVC), and its external dimensions match those of the downstream flow equalization plate.

[0099] The honeycomb rectifier is installed close to the upstream side of the downstream flow equalization plate. When the electroplating solution flows through the rectifier, the transverse velocity component in the fluid is eliminated under the action of the parallel channels, and the flow direction is forcibly adjusted to be parallel to the channel axis, thereby forming a uniform laminar flow. The rectified electroplating solution then enters the next flow field region through the through holes of the downstream flow equalization plate, ensuring that the next flow field region operates under stable inlet conditions.

[0100] The orifice ratio of the rectifier can be designed according to process requirements, typically ranging from 30% to 60%. Too low an orifice ratio will increase flow resistance, while too high an orifice ratio will reduce rectification efficiency.

[0101] In some other implementations, the top of the buffer zone is provided with a bubble collection and discharge structure to prevent tiny bubbles carried by the previous flow field region from entering the next flow field region and adhering to the surface of the circuit board or inside the holes.

[0102] In this embodiment, the bubble collection and discharge structure includes a gas collection hood and an exhaust valve. The gas collection hood is located at the top of the pressure buffer chamber and has an inverted conical or sloping structure, with its lowest point connected to the exhaust valve. The slope angle of the gas collection hood is 15° to 30°, utilizing the buoyancy of the bubbles to automatically gather them upwards to the top of the gas collection hood.

[0103] In some embodiments of this application, the electroplating method described above may further include: applying a forward-reverse switching current to the circuit board, wherein the forward-reverse switching current may include alternately applied forward electroplating current and reverse pulse current. The forward electroplating current is used to achieve copper deposition, and the reverse pulse current is used to dissolve the excessively deposited copper layer near the aperture in a very short time, level the aperture, and replenish the aperture with fresh electroplating solution and additives.

[0104] In some embodiments of this application, the forward-reverse switching current is synchronized with the application timing of the first flow field or the second flow field, wherein: when the first flow field is applied, the forward-reverse switching current operates with a first forward current density, a first reverse current density, a first frequency, a first forward pulse width, and a first reverse pulse width; when the second flow field is applied, the forward-reverse switching current operates with a second forward current density, a second reverse current density, a second frequency, a second forward pulse width, and a second reverse pulse width.

[0105] Specifically, when the first flow field forms the first directional electroplating liquid flow on both sides of the circuit board, the forward and reverse switching current operates with the first set of parameters. In the second flow field, the forward and reverse switching current operates with the second set of parameters. The first forward current density is lower than the second forward current density, thus using a lower current in the first flow field to avoid edge clamping or internal breakage due to excessively low TP value. The second flow field uses a higher current to increase the current density and compensate for the internal thickness of the hole. Correspondingly, the first reverse pulse width and the first frequency are also lower than the second reverse pulse width and the second frequency of the second flow field, respectively.

[0106] It should be noted that in some embodiments of this application, the current density of the first reverse pulse current is 1 to 5 times the first forward electroplating current density, and the pulse width of the first forward electroplating current is 5 to 20 times the pulse width of the first reverse pulse current. The determination of this parameter range is based on the following technical considerations: Lower limit of reverse current density (1 time): When the reverse current density is lower than the forward current density, the reverse pulse's dissolution effect on the excessively deposited layer at the orifice is insufficient, failing to effectively level the orifice, resulting in limited improvement in TP value; Upper limit of reverse current density (5 times): When the reverse current density exceeds 5 times the forward current density, the reverse pulse may excessively dissolve the deposited layer on the orifice wall, or even damage the base plating layer, leading to discontinuity or decreased adhesion of the plating layer within the orifice; Lower limit of pulse width ratio (5 times): When the ratio of the forward pulse width to the reverse pulse width is less than 5 times, the reverse pulse duration is relatively too long, easily causing excessive dissolution at the orifice and forming "pit" defects. Pulse width ratio upper limit (20 times): When this ratio is higher than 20 times, the reverse pulse duration is relatively too short, the leveling effect is not obvious, and the forward pulse is too long, which may lead to an increase in the additive consumption gradient in the hole. Similarly, the current density of the second reverse pulse current is 1 to 5 times the current density of the second forward electroplating current, and the pulse width of the second forward electroplating current is 5 to 20 times the pulse width of the second reverse pulse current.

[0107] For example, when the second flow field forms a symmetrical convection field on both sides of the circuit board for thickening electroplating, the second forward current density is set to 2.0 A / dm², and the second reverse pulse current density is set to 3.0 A / dm² (1.5 times that of the forward). The second reverse pulse width is 10 ms, the second forward pulse width is 100 ms (10 times that of the reverse), and the pulse frequency is 9.1 Hz. The second flow field forms turbulence within the hole, which enhances mass transfer to a certain extent. The forward current utilizes the already established efficient mass transfer conditions within the hole to uniformly deposit copper ions on the hole wall. The reverse current can precisely dissolve the excessive deposition layer formed near the hole opening due to current concentration.

[0108] Correspondingly, when the second flow field forms an alternating unidirectional flow field on both sides of the circuit board, the flow is switched to the other side after spraying for 10 seconds on each side, forming a periodically alternating unidirectional pulse flow. At this time, the second forward electroplating current density is set to 1.8 A / dm², and the second reverse pulse current density is set to 4.5 A / dm² (2.5 times that of the forward direction). The width of the second reverse pulse is 5 ms, and the width of the second forward pulse is 100 ms (20 times that of the reverse direction), with a pulse frequency of 9.5 Hz. At this time, the solution completely penetrates the via from one side to the other. Due to the higher flow velocity of unidirectional flow, the mass transfer efficiency within the via is better than that of double-sided convection. At this time, the second reverse pulse current is applied, and its current density is relatively high (2.5 times that of the forward direction) to cope with the more significant current concentration effect at the via opening. The narrow width of the second reverse pulse (5 ms) ensures that only the extremely thin layer at the via opening is dissolved, without damaging the base plating layer already deposited on the via wall.

[0109] In some embodiments of this application, the base plating layer is a continuous conductive layer with a thickness of at least 0.5 μm. This base plating layer is a continuous conductive layer deposited on the wall of a via in the circuit board by a first flow field, preferably ranging from 1 μm to 3 μm. When the thickness of the base plating layer reaches 0.5 μm, a continuous conductive network is formed on the surface of the via wall. At this time, the electric field can extend uniformly from the board surface to the depth of the via, providing a conductive basis for the subsequent thickening electroplating by the second flow field. If the thickness of the base plating layer is less than 0.5 μm, there may be tiny discontinuities or insulating areas on the via wall, resulting in uneven electric field distribution and "breakpoints" or "voids" in the deposition within the via.

[0110] In some embodiments of this application, the aspect ratio of the high aspect ratio through-hole ranges from 20:1 to 50:1. Within this range, the TP value is ≥85%, with a maximum TP value reaching 95%. Different pushing processes can be selected depending on the through-hole aspect ratio: for aspect ratios of 20:1 to 30:1, the second flow field preferentially selects a convective electroplating solution flow field, combined with forward and reverse conversion current, balancing TP value and production efficiency; for aspect ratios of 30:1 to 40:1, the second flow field can be a convective electroplating solution flow field or an alternately applied unidirectional flow field, balancing the requirements for board surface uniformity; for aspect ratios of 40:1 to 50:1, the second flow field preferentially selects an alternately applied unidirectional flow field, combined with a forward and reverse conversion current with a higher reverse current density, ensuring thorough replacement of the chemicals within the hole. For examples, see the appendix. Figure 7 Taking a 10mm thick circuit board as an example, Figure 7 The diagram shows the electroplating effect in the orifice area and the center area of ​​the orifice. The orifice diameter is 200μm, the average plating thickness is 30μm, the plating difference is <5μm, the average copper plating thickness is 35μm, and the TP value is 85.7%.

[0111] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because based on this application, some steps can be performed in other orders.

[0112] like Figure 8 The diagram shown is a schematic of a controller provided in an embodiment of this application. Specifically, the controller 20 may include: a processor 200, a memory 201, and a computer program 202 stored in the memory 201 and executable on the processor 200, for example, an electroplating process for a circuit board with high aspect ratio vias. When the processor 200 executes the computer program 202, it implements the steps in the above embodiments of the electroplating method for circuit boards with high aspect ratio vias, for example... Figure 1 Steps S101 to S103 are shown.

[0113] The computer program can be divided into one or more modules / units, which are stored in the memory 201 and executed by the processor 200 to complete this application. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the controller.

[0114] The controller may include, but is not limited to, a processor 200 and a memory 201. Those skilled in the art will understand that... Figure 8This is merely an example of a controller and does not constitute a limitation on the controller. It may include more or fewer components than illustrated, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0115] The processor 200 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0116] The memory 201 can be an internal storage unit of the controller, such as the controller's hard drive or memory. The memory 201 can also be an external storage device of the controller, such as a plug-in hard drive, Smart Media Card (SMC), Secure Digital (SD) card, or FlashCard. Furthermore, the memory 201 can include both internal and external storage units of the controller. The memory 201 is used to store the computer program and other programs and data required by the controller. The memory 201 can also be used to temporarily store data that has been output or will be output.

[0117] It should be noted that, for the sake of convenience and brevity, the structure of the controller described above can also be referred to the specific description of the structure in the method embodiment, which will not be repeated here.

[0118] Specifically, Figure 9 This application also provides an electroplating apparatus, comprising: The electroplating apparatus 10 includes a first processing section and a second processing section arranged sequentially along the conveying direction of the circuit board; wherein the first processing section can be used to form a first flow field, and the second processing section can be used to form a second flow field. The controller 20, connected to the electroplating apparatus 10, is used to execute the steps of the electroplating method for circuit boards with high aspect ratio through holes provided in this application. Specifically, the controller 20 controls the circuit board to move along the conveying direction to sequentially pass through a first processing section and a second processing section.

[0119] In some embodiments of this application, the electroplating apparatus 10 further includes a third processing section arranged downstream of the second processing section along the conveying direction, the third processing section being used to form a third flow field.

[0120] In some embodiments of this application, the electroplating apparatus 10 may include an electroplating tank, and the first processing section, the second processing section and the third processing section may be disposed in the electroplating tank.

[0121] In some embodiments of this application, the electroplating apparatus 10 further includes a buffer zone comprising an upstream flow baffle plate disposed downstream of the first processing section; a downstream flow equalization plate disposed upstream of the second processing section; and a pressure buffer chamber formed between the upstream flow baffle plate and the downstream flow equalization plate.

[0122] In some embodiments of this application, the second processing section includes: multiple sets of spray units symmetrically arranged on both sides of the circuit board thickness direction, and the nozzles on the spray units on both sides are staggered in the vertical direction; and a liquid supply system for supplying electroplating solution to the spray units.

[0123] In some other embodiments of this application, the second processing section includes: two sets of spraying units, respectively disposed on both sides of the circuit board in the thickness direction; and a timing controller for controlling the two sets of spraying units to work alternately, so that only one set of spraying units sprays electroplating liquid onto the circuit board surface at any given time.

[0124] In some embodiments of this application, the second processing section further includes: a forward-reverse current converter connected to the circuit board, for applying a forward-reverse conversion current to the circuit board, the forward-reverse conversion current including alternately applied forward pulse current and reverse pulse current; and a timing controller for synchronizing the application timing of the forward-reverse conversion current and the second flow field.

[0125] Furthermore, this application also provides a circuit board including an interconnect structure, wherein the interconnect structure is obtained by electroplating based on the electroplating method provided in this application for circuit boards with high aspect ratio through holes, or based on... Figure 9 It is made using the electroplating equipment shown.

[0126] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0127] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0128] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for various specific applications, but such implementations should not be considered beyond the scope of this application.

[0129] In the embodiments provided in this application, it should be understood that the disclosed devices / controllers / systems and methods can be implemented in other ways. For example, the device / controller / system embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0130] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected based on actual needs to achieve the purpose of this embodiment.

[0131] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0132] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed based on the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, based on legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0133] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An electroplating method for a circuit board with through holes, characterized in that, include: The circuit board is immersed in the electroplating solution and transported along a predetermined path; A first flow field is applied to the circuit board to form a base plating layer on the wall of the through hole of the circuit board, thereby giving the circuit board a first TP value; wherein, the first flow field includes a plurality of first directional electroplating liquid flows penetrating the through hole, the first directional electroplating liquid flows having a first pressure difference, and the thickness of the base plating layer is within a first predetermined threshold range; A second flow field is applied to the circuit board having the base plating layer, thereby giving the circuit board a second TP value; the second flow field includes a plurality of second directional electroplating liquid flows having a second pressure difference; Wherein, the second pressure difference is less than the first pressure difference, and the second TP value is greater than the first TP value.

2. The electroplating method according to claim 1, characterized in that, The first directional electroplating liquid flow penetrates the through hole by a first pressure difference generated at both ends of the through hole through the combined action of spraying and suction, and the first pressure difference has a first pressure difference value; The second directional electroplating liquid flow acts on the circuit board by spraying, and the resulting unsteady pressure gradient forms a second pressure difference, which is within the range of the second pressure difference. The maximum value of the second differential pressure range is less than the first differential pressure value.

3. The electroplating method according to claim 1, characterized in that, Along the conveying direction of the circuit board, the axial centers of adjacent first directional electroplating liquid flows have a first distance D1 and flow in opposite directions, and the axial centers of adjacent second directional electroplating liquid flows have a second distance D2, where D2≤D1.

4. The method according to claim 3, characterized in that, In the first flow field, the time difference between the through holes of the circuit board receiving the action of adjacent first directional electroplating liquid flows is the first time difference TD1, and the time difference between the through holes of the circuit board receiving the action of adjacent first directional electroplating liquid flows is the second time difference TD2, where TD1≤TD2.

5. The method according to claim 1, characterized in that, The second flow field is a convective electroplating solution flow field applied simultaneously from both sides of the circuit board thickness direction to the surface of the circuit board, and the second flow field acts on the entire surface of the circuit board and the through holes; or, The second flow field is a unidirectional flow field that is alternately applied along the thickness direction of the circuit board. The unidirectional flow field is used to apply a directional electroplating liquid flow from one side to the other side of the thickness direction of the circuit board at any given time, and the flow direction is periodically switched.

6. The method according to claim 5, characterized in that, After applying a second flow field to the circuit board having the base plating, the method further includes applying a third flow field to the circuit board. The third flow field is the same as the first flow field, or, The third flow field is the same as the second flow field.

7. The method according to claim 1, characterized in that, The first flow field applied to the circuit board has a first duration T1, and the second flow field applied to the circuit board having the base plating has a second duration T2, where T1≤T2.

8. The method according to claim 1, characterized in that, The method further includes: Detect the current plating thickness in the through-hole of the circuit board; Based on the current coating thickness, the circuit board is controlled to move along the conveying direction to switch between the first flow field and the second flow field.

9. The method according to claim 8, characterized in that, The detection of the current plating thickness in the through-hole of the circuit board includes: When the circuit board is in the area affected by the first flow field, the coating thickness of the through hole wall is periodically detected. When the circuit board is in the area affected by the second flow field, the coating thickness of the through hole wall is periodically measured.

10. The method according to claim 9, characterized in that, The step of controlling the circuit board to move along the conveying direction based on the current plating thickness specifically includes: If the thickness of the first detected coating is lower than the lower limit of the first predetermined threshold range, then the circuit board is controlled to reduce the conveying speed or stop conveying. If the thickness of the first detected coating is higher than the upper limit of the first predetermined threshold range, then the circuit board is controlled to increase its conveying speed.

11. The method according to claim 1, characterized in that, A buffer zone is provided between adjacent flow fields along the conveying direction of the circuit board, the buffer zone comprising: An upstream baffle plate is placed downstream of the previous flow field region to block the transmission of pressure fluctuations. The downstream flow equalization plate is located upstream of the next flow field region and is used to equalize the electroplating liquid flow entering the next flow field. A pressure buffer chamber is formed between the upstream flow baffle and the downstream flow equalization plate to buffer pressure fluctuations.

12. The method according to claim 1, characterized in that, Also includes: A forward-reverse switching current is applied to the circuit board, the forward-reverse switching current including an alternately applied forward plating current and a reverse pulse current.

13. The method according to claim 12, characterized in that, The forward and reverse conversion current is synchronized with the application timing of the first flow field or the second flow field, wherein: When the first flow field is applied, the forward-reverse switching current operates with a first forward current density, a first reverse current density, a first frequency, a first forward pulse width, and a first reverse pulse width; When the second flow field is applied, the forward-reverse switching current operates with a second forward current density, a second reverse current density, a second frequency, a second forward pulse width, and a second reverse pulse width; The first forward current density is less than the second forward current density.

14. The method according to claim 13, characterized in that, The first reverse current density is 1 to 5 times the first forward current density, and the pulse width of the first forward pulse current is 5 to 20 times the pulse width of the first reverse pulse current.

15. The method according to claim 1, characterized in that, The first flow field is formed in the following way: The parameters of the spray unit and the suction unit, which are staggered on both sides of the thickness direction of the circuit board, are controlled so that the spray unit and the suction unit on both sides are arranged in a spray-suction correspondence. The electroplating liquid flow sprayed from the spray unit on one side passes through the through hole under the spray-suction pressure difference and is sucked in by the corresponding suction unit on the opposite side to form the directional electroplating liquid flow. Along the conveying direction of the circuit board, adjacent spray units and suction units are staggered so that the flow directions of adjacent directional electroplating liquid flows are opposite.

16. The method according to claim 1, characterized in that, The second flow field is formed in the following way: Multiple spray units symmetrically arranged on both sides of the thickness direction of the circuit board simultaneously spray electroplating liquid onto the surface of the circuit board, forming a double-sided convective electroplating liquid flow field. The nozzles on the spray units on both sides are staggered in the thickness direction of the circuit board.

17. The method according to claim 1, characterized in that, The second flow field is formed in the following way: By controlling the timing, the spray units on both sides of the circuit board in the thickness direction work alternately. At any given time, only one side of the spray unit sprays electroplating liquid onto the circuit board surface, while the other side's spray unit or suction unit is in a closed or suction state, thereby forming a unidirectional flow field with periodically alternating flow direction.

18. The method according to any one of claims 1-15, characterized in that, The base coating is a continuous conductive layer with a thickness of at least 0.5 μm.

19. The method according to any one of claims 1-16, characterized in that, The aspect ratio of the through hole ranges from 20:1 to 50:

1.

20. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1-17.

21. An electroplating device, characterized in that, include: An electroplating apparatus, comprising a first processing section and a second processing section arranged sequentially along the conveying direction of the circuit board; The first processing section is used to form a first flow field, and the second processing section is used to form a second flow field; A controller, connected to the electroplating apparatus, is used to perform the steps of the method as described in any one of claims 1 to 19.

22. A circuit board, characterized in that, It includes an interconnect structure, which is obtained by electroplating a circuit board with through holes according to any one of claims 1 to 19, or is made by electroplating equipment according to claim 21.

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